Vibratory motor and controlled circuit for a small timepiece



Oct. 19, 1965 AKIRA NAKAI VIBRA'IORY MOTOR AND CONTROLLED CIRCUIT FOR ASMALL TIMEPIECE' 5 Sheets-Sheet 1 Filed June 4, 1965 TIME DISR MECHANISMSYNCHRO. MOTOR FREQUENCY DI v: DER

C RYSTAL OSCILLAT INVENTOR.

AKIRA NAKAl Oct. 19, 1965 AKIRA NAKAI 3,212,252

VIBRATORY MOTOR AND CONTROLLED CIRCUIT FOR A SMALL TIMEPIECE Filed June4, 1963 5 Sheets-Sheet a INVENTOR.

AKIRA NAKM Oct. 19, 1965 AKIRA NAKAI 3,212,252

VIBRATORY MOTOR AND CONTROLLED CIRCUIT FOR A SMALL TIMEPIECE Filed June4, 1963 5 Sheets-Sheet 5 I DRIyE CIRCUIT} G-EAR MECHAN. 400 200 TW TUNERFLIP'F c5 FLIP Her I l I L /5(NOHRONOU8 MOTOR INVENTOR.

AKHZA NAKM Oct. 19, 1965 K R KA 3,212,252

VIBRATORY MOTOR AND CONTROLLED CIRCUIT FOR A SMALL TIMEPIEGE Filed June4, 1963 5 Sheets-Sheet 4 INVENTOR.

AK lRA NAKAl Oct. 19, 1965 AKIRA NAKAI 3,212,252

RRRRRRRRRRRRRRRRRRRRRRRRR ED I UIT FOR A SMALL TIMEPIECE Filed June 4,1965 5 Sheets-Sheet 5 b ll N 1 NW WWHHHHH l HHHHHHMMMHUHHHHMHHMLUHHUHULLIJHHIJL c J P F F F TY T W] WIT r WU J J J Hi JLULHLUL 4 JUL d F r- 7 FT l T F r i J J| JU 4 AU WWW]WWWh INVENTOR. AKl RA NA KM United StatesPatent 3,212,252 VIBRATORY MOTOR AND CONTROLLED CIRCUIT FOR A SMALLTIMEPIECE Akira Nakai, Tokyo, Japan, assignor to Citizen Tokei KabushikiKaisha, Tokyo, Japan, a corporation of Japan Filed June 4, 1963, Ser.No. 285,348 3 Claims. (Cl. 5823) This invention relates to smalltimepieces having crystal oscillators for their time base. In this typeof timepiece, generally speaking, electrical output from the crystaloscillator is supplied to a frequency divider and thence amplified by apower amplifier so as to energize a synchronous motor which drives aconventional time display mechanism.

Electrical circuits employed for this purpose make use ofsemiconductors, especially transistors, for the purpose of reducingoverall size of the timepiece, as Well as the power consumption of thecircuit. With conventional techniques, however, the power consumption isstill relatively high so that battery-powered small crystal timepieceshave not yet been a commercial reality.

It is one of the objects of the present invention to provide anefiicient small timepiece having as its time base a crystal oscillatorand a synchronous motor driven therefrom.

It is another object of the invention to provide a small battery-poweredcrystal timepiece capable of operating for a long period of time on asmall capacity battery.

It is still another object of the invention to provide a smallbattery-powered timepiece which provides a negligibly small positionerror and thus operates with a high accuracy.

It is a still further object of the invention to provide a smallbattery-powered crystal timepiece which is simple in its design andeconomic in its manufacture.

These and other objects of the invention will be more apparent to thoseskilled in the art from a consideration of the following detaileddescription when taken together with the accompanying drawings in which:

FIG. 1 represents a block diagram illustrating the timepiece accordingto this invention;

FIG. 2 represents a perspective view of essential parts of the timepiecemechanism of the aforementioned timepiece, with the electricalconductors and the conventional gear train omitted from the drawing forsimplicity;

FIG. 3 represents an enlarged view of several parts of FIG. 2,illustrating more clearly the mechanical oscillator which iselectromagnetically driven;

FIG. 4 represents a top plan view of the mechanism shown in FIG. 2;

FIG. 5 represents a perspective view of the mechanical oscillator;

FIG. 6 represents a block diagram showing the energy transmission in thenovel mechanism by way of example;

FIG. 7 is a circuit diagram showing electronic constituents embodied inthe invention by way of example;

FIG. 8, p to 1', represents voltage curves of the driving energy of themechanical tuner employed in this invention with the tuner operating atsynchronized condition;

FIG. 9 represents voltage curves at various stages of the mechanismaccording to the invention, and;

FIG. 10 is an enlarged side view of a part of the rotor magneticallycooperating with the vibrator.

Referring now to the accompanying drawings, especially FIG. 1 thereof,the timepiece mechanism construced according to the novel teachings ofthe invention comprises generally a crystal, preferably quartzoscillator 1, a frequency divider 2, a synchronous motor 3 having amechanical vibrator such as mechanical tuner, and a conventional timedisplay mechanism 4.

The synchronous motor 3 comprises, as shown in FIGS. 2-5, a mechanicaltuner or vibrator 5 and a rotor 6 magnetically coupled therewith forbeing driven therefrom. The vibrator comprises a resilient strip magnet7 having a generally rectangular shape internally punched and providedwith a front gap 7a providing a pair of oppositely arranged, inwardlydirecting pole formations 7b and 7c closely embracing the rotor 6 fromits both sides. At the outboard or right-hand end of the magnet 7, aspring strip 10 is fixedly attached as by sticking, fusion Welding,riveting or the like. As shown, the spring strip is shaped into a closedE, the central lead of which is fixedly mounted on a bracket 11 by meansof set screws 12. The thus provided spring-magnet assembly 5 is fixedlyattached at its outboard end with a pair of oppositely arranged magnetpieces 8 and 9. These pieces are made preferably into short rigidcylinders as shown. The bracket is in turn fixedly mounted on framework13 of the timepiece mechanism. As will be described more in detailhereinafter, the thus provided vibrator makes oscillatory movement aboutan imaginary axis XY passing through a point between set screws 12. Thevibrator is so shaped and dimensioned that the center of gravity of thewhole mass of the vibrator is substantially on the aforementioned axis.

The rotor 6 has spokes 14 having arched apertures 15. Radially in linewith these arched apertures are outer tooth-like projections 16 whichare separated by U'shaped recesses 17. As shown in FIG. 10 by dottedlines 18, a wavy track will be produced along the rim of the rotor whichis rotatably supported on the framework 13 so as to magneticallycooperate with the aforementioned pole formations 7b and 7c. Rotor 6 isrotatably mounted in the framework 13 and drivingly connected with aconventional gear train 2130 of the timepiece mechanism, the said geartrain being shown, especially in FIG. 4.

A pair of sensing and drive coils 19 and 20 are mounted through propersupports 31 and 32 on framework 13. It will be seen especially from FIG.4, magnet pieces 8 and 9 are concentrically arranged relative to thesesensing and drive coils with small air gaps between them.

The coil 20 is rigidly mounted on a cantilevered support 32 fixedlyattached to the framework. The fixing means are not shown. Through abore of this support 32, as well as through a bore in the flange 34 of abracket 35 fixedly mounted on framework 13, a pointed follower pin 33passes without interference. The pin is provided with a stop 35 and acoil spring 36 inserted between flange 34 an stop 35 under compressionso that pin 33 is urged to move downwards so as to keep pressure contactwith a cam 37 which is rotatably mounted on bracket 35 and framework 13.Although not shown, cam 37 is provided with a knob so that bymanipulating the latter the cam can be rotated in one direction oranother to elevate or lower the follower pin 33 for the purpose ofadjusting the magnetic performance of the drive magnet assembly. Forthis purpose, the pin 33 is provided at its top end with an auxiliarymagnet piece which is arranged to cooperate magnetically with the maindrive magnet piece 9, as will be described in detail hereinafter. Inthis way, the oscillating characteristics of the vibrator 5 can beadjusted to meet environmental requirements.

A manual starter of segmental gear type is provided. The segmental gear38 is rotatably mounted on frame work 13 and provided with a knob 40fixed on the outboard end of the shaft 39 rigidly connected with thesegment. Urging spring 41 is fitted to the segment and urges to rotatethe segment in the disengaging direction from pinion 42 fixedly mountedon the shaft of rotor 6.

A more detailed block diagram of the timepiece according to thisinvention is shown in FIG. 6. FIG. 7 represents a circuit diagramshowing a preferred combination of electrical parts employed.

Crystal oscillator 1 includes, by Way of example as shown in FIG. 7, aconventional quartz oscillator 43 energized from a DC. current source44; a transformer 45; transistors 46 and 47; and a plurality ofcondensers and resistors. This crystal oscillator circuit is of ratherconventional design and designed to deliver a 3.2 kc. output, the waveform of which is shown schematically at a in FIG. 9. This output issupplied to a conventional Schmitt circuit 48 comprising transistors 49and 50 and transformed into a corresponding rectangular wave as shown atb in FIG. 9. The provision of this Schmitt circuit 48 serves effectivelyfor obtaining an accurate and maintained rectangular wave even when thebattery voltage should have been considerably reduced. The rectangularwave voltage thus produced is delivered to a first stage flip-flopcircuit 51 including diodes 52-53, transistors 54-55, and theconventionally arranged resistors and condensers, whereby the frequencyof the delivered voltage is reduced to 1.6 kc., or to half the inputfrequency, as shown at c in FIG. 9. The frequency divider circuit 2comprises five such flip-flop stages 51, 56, 57, 58 and 59, for dividingthe voltage frequency by two at each stage thereof, as shown d-g in FIG.9. Thus, from the last flip-flop stage 59, a 100 cycle square wave isobtained and supplied to a drive circuit 69 of the synchronous motor 3.This circuit includes aforementioned two sensing and drive coils 19-20,condensers c1, c2 and c3, resistors R1, R2 and R3, transistor Tr andbattery 44. The sensed and driving voltages in the both coils 19-20 areshown at h and i in FIG. 9, respectively, from which it will be seenthat these voltages are in opposite phases to each other. Additionally,second and further flip-flops 56-59 are shown simply by dotted blocksfor the simplicity of the drawing. Further, the natural frequency of thespring-magnet assembly is so selected that it is practically same as thefrequency of the drive current for drive coil 20, that is 100 cycles persecond in this preferred embodiment.

The working principle employed by the mechanical vibrator and rotormagnetically coupled therewith is already known as shown by U.S. Patent2,841,986 granted July 8, 1958 to C. F. Clifford, which disclosesmechanical oscillators designed for timepiece escapements. The prior artdiscloses that the vibrator is used for controlling the stepwiserotation of the rotor magnetically coupled therewith, which rotor isdriven mechanically from a mechanical power source such as aconventional power spring embodied in a mechanical timepiece. A uniquefeature of the present invention is the elimination of the power springand the employment of a synchronous motor comprising the spring-magnetassembly powered in the aforementioned way from a crystal oscillatorwhich is in turn powered from a battery contained in the timepiece, onthe one hand, and a rotor magnetically coupled with the vibratorassembly and having a wavy magnetic track as shown by dotted lines 18 inFIG. 10, on the other hand.

When it is desired to let the timepiece run, the vibrator assembly isbrought into actuation in the aforementioned way at a frequency of 100cycles per second in this case. Next, knob 40 is manually turned againstthe action of spring 41 until segmental gear 38 is brought intoengagement with pinion 42 which is fixedly attached on the shaft ofrotor 6. When the knob is released, the spring 41 will release itsaccumulated power through the intermediary of gear segment 38 so as toturn the pinion 42 with its shaft and rotor 6 in a predetermineddirection. The provision of this manual starter is for the purpose of aneasy starting of the synchronous motor, on the one hand, and for theprevention of otherwise possible reverse rotation of the motor. Asalready mentioned, the natural frequency of the mechanical vibrator isselected to be substantially equal to the frequency of the current fedto the vibrator, the motor will start running after a short timeinterval at a stable resonant frequency, more specifically at cycles persecond in this embodiment. Since the center of gravity of whole mass ofthe vibrator is placed substantially on the vibrating axis X-Y asalready described, the vibrating system is well balanced so that thepower consumption can be minimized as will be described hereinafter by anumerical example. Thanks to this arrangement, position errors of thetimepiece can be also minimized.

If for some reason, the frequency of the vibrator becomes ditferent fromthe design frequency thereof, cam 37 is manually turned by means of theknob (not shown) attached fixedly to the cam shaft so as to elevate orlower, as the case may be, the auxiliary magnet (not shown) attached tothe top end of pin 33. If the auxiliary magnet has a magnetic polarityopposite'to that of the drive magnet piece 9 and the former is broughtnearer to the latter, the vibrator is somewhat accelerated, and viceversa. This adjusting means is principally employed for examinationpurpose while manufacturing a number of vibrators in a factory. Thus,practical timepieces can be dispensed with such means.

When the vibrator oscillates at a predetermined frequency, the rotor 6is stepwise rotated in its predetermined advancing direction and thusrotation is transmitted therefrom through conventional gear train 21-30mechanically connected to the conventional time display mechanism as at4 which comprises a short hand, a long hand, a second hand and atimepiece dial carrying time symbols, all not shown.

It Will thus be understood that when the quartz oscillator 43 isenergized, the rotor 6 is rotated stepwise and the time is displayed bymeans of time indicator 4.

If necessary, Schmitt circuit 48 may be displaced by any conventionalelectronic circuit which is capable of converting a sinusoidal electriccurrent into a corresponding rectangular one, although Schmitt circuitis highly recommended by reason of its high reliability and stableperformance even with changes of the supplied voltage.

In this invention, a plurality of series-connected flipfiops 51, 56-59are employed for the purpose of frequency division as describedhereinbefore. This arrangement is highly recommendable for its highstability when subjected to possible gradual changes either or both inthe ambient temperature of the atmosphere and the working voltagesupplied from the source.

In practice, however, the series-connected flip-flops can be displacedby other conventional frequency dividers.

In the course of the operation of the timepiece in the above-mentionedway, an input current, at 100 c./s., is supplied from the last stageflip-flop 59 to drive circuit 60. The input side of transistor Tr incombination with resistors R1 and R2 constitutes an AND-circuit, so thatthe base of the transistor is supplied with the sum of the voltageinduced in the sensing coil 19 by the vibratory movement of the vibrator5, and a constant frequency voltage supplied from the last stageflip-flop 59. Thus, by adjusting resistors R1 and R2, the vibrator canbe brought into a synchronous oscillation to the frequency of the drivecurrent from the last stage flip-flop so that the vibrator may perform astable oscillatory motion under resonant conditions. With use of thisdrive circuit, the frequency of the vibrator can be controlled at theinput side of the transistor circuit by means of the signal output fromthe flip-flop assembly, which signal output may be of relatively smallvalue. Thanks to this arrangement, a highly stable operation of theflip-flop assembly can be assured.

In operation, when the flip-flop assembly is disconnected from the drivecircuit 60, the vibrator will operate at its own natural frequency andthus inspection and adjustment of the natural frequency characteristicof the vibrator can be easily accomplished. Transistor Tr may preferablybe of the p-n-p junction type and resistor R3 acts as biasing means forit. C1 and C2 are coupling condensers and C3 is a condenser inserted inthe circuit so as to suppress a possible high frequency oscillationcaused by the electrical combination of sensing and drive coils 19-20.

Voltage curves of the fed current to the vibrator constr-ucted accordingto the present invention are shown in FIG. 8, p, q and r, respectively.The curve at p is that will appear across the drive coil 20 when thenatural frequency of the vibrator is somewhat lower than the frequencyof the fed current, that is 100 c./s. in this case. The curve at q isobtained with the both frequencies precisely in coincidence with eachother, while the curve shown at r applies to the case in which thenatural frequency is somewhat higher than the frequency of the fedcurrent.

With use of the aforementioned synchronous motor having a mechanicalvibrator capable of operating at a resonant frequency, a higherelectrical efficiency can be obtained. This, it will generally be about30%, While that of a conventional comparative synchronous motor is aboutExample As drive coil, 3800 turns of insulated copper wire, 50 dia. wereemployed. The sensing coil had equally 3800 turns of 40 dia. insulatedcopper wire. Each of the magnet pieoes was made from a magnetic alloy ofAlnicoseries PFII supplied by a Japanese firm, Nihon Jishaku KabushikiKaisha, Tokyo, Br: 12,50013,000; H0: 580- 650. The vibrating magnet:Vicalloy, 10 X 25 x .24 mm. The supporting spring: =Elinvar, 8.5 X 5.8 X.27 mm. The rotor: soft iron; DD. mm.; No. of teeth: 20.

Output of quartz oscillator: 3.2 kc. Output of Schmitt circuit: 3.2 kc.Outputs of first and last stage flip fiops: 800 and 100 c./s.,respectively. Current source: 1.5 v.

With the above specifications of the constituent parts, the powerconsumption of the synchronous motor amounted to 0.5 ma. Power requiredfor the electronic circuits including quartz oscillator, Schmitt circuitand five stages of flip-flop: 1.0 ma. Thus, overall power consumption ofthe timepiece mechanism: 1.5 ma.

The above mentioned novel timepiece mechanism operated satisfactorilyunder variable ambient temperature conditions ranging from 0 to +40 C.

Without further analysis, the foregoing will sofully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention,and therefore, such adaptations should and are understood to be withinthe meaning and range of equivalents of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a timepiece, the combination comprising a crystal oscillator, avibrating means for movement of time display elements of the timepiecewith vibration thereof, an electromagnetic drive means for vibratingsaid vibrating means, first signalling means actuated by said crystaloscillator for providing rectangular wave form signals having afrequency substantially the same as the natural frequency of vibrationof said vibrating means, second signalling means for detecting thevibrations of said vibrating means and providing signals indicativethereof, and electric circuit means for feeding the first-mentionedsignals summed with the second-mentioned signals to the electromagneticdrive means whereby deviations from the resonant frequency of vibrationof said vibrating means are immediately detected and corrected.

2. The timepiece of claim 1 wherein said vibrating means aremagnetically coupled to a rotor having an irregular magnetic track whichwhen acted upon by the vibrational forces of said vibrating meanstransmitted through the magnetic coupling causes said rotor to rotate.

3. The timepiece of claim 1 wherein said first signalling means includesfrequency divider means interposed between the crystal oscillator andthe electromagnetic drive means for reducing a higher frequency signaloriginated by the crystal oscillator to a lower frequency signalsubstantially the same as the natural frequency of vibration of saidvibrating means.

References Cited by the Examiner UNITED STATES PATENTS 2,571,085 10/51Clifford 5823 2,606,222 8/52 Clifford et al. 5 8-23 2,624,017 12/52Putnocky 3 10-46 2,852,725 9/58 Clifford 318128 2,976,470 3/61Krassoievitch et al. 318--341 3,011,111 11/61 Clifiord 5823 FOREIGNPATENTS 712,445 6/31 France.

LEO SMILOW, Primary Examiner. JOSEPH P. STRIZAK, Examiner.

1. IN A TIMEPIECE, THE COMBINATION COMPRISING A CRYSTAL OSCILLATOR, AVIBRATING MEANS FOR MOVEMENT OF TIME DISPLAY ELEMENTS OF THE TIMEPIECEWITH VIBRATION THEREOF, AN ELECTROMAGNETIC DRIVE MEANS FOR VIBRATINGSAID VIBRATING MEANS, FIRST SIGNALLING MEANS ACTUATED BY SAID CRYSTALOSCILLATOR FOR PROVIDING RECTANGULAR WAVE FORM SIGNALS HAVING AFREQUENCY SUBSTANTIALLY THE SAME AS THE NATURAL FREQUENCY OF VIBRATIONOF SAID VIBRATING MEANS, SECOND SIGNALLING MEANS FOR DETECTING THEVIBRATION OF SAID VIBRATING MEANS AND PROVIDING SIGNALS INDICATIVETHEREOF AND ELECTRIC CIRCUIT MEANS FOR FEEDING THE FIRST-MENTIONEDSIGNALS SUMMED WITH THE SECOND-MENTIONED SIGNALS TO THE ELECTROMAGNETICDRIVE MEANS WHEREBY DEVIATIONS FROM THE RESONANT FREQUENCY OF VIBRATIONOF SAID VIBRATING MEANS ARE IMMEDIATELY DETECTED AND CORRECTED.